About Our Calculator
How we calculate child maintenance using the official CMS formula
How It Works
Our calculator uses the exact same formula as the Child Maintenance Service (CMS). This formula has been in use since 2012 and takes into account the paying parent's gross income, the number of children, shared care arrangements, and other factors.
The CMS Formula
Step 1: Calculate Weekly Income
Your gross annual income is divided by 52 to get your weekly income. Pension contributions are deducted from this amount.
Step 2: Apply Rate Band
- Nil Rate: Below £7/week - No maintenance payable
- Flat Rate: £7-£100/week - Fixed £7/week
- Reduced Rate: £100-£199/week - Sliding scale
- Basic Rate: £200-£800/week - 12% (1 child), 16% (2 children), 19% (3+ children)
- Basic Plus: Over £800/week - Additional 9%, 12%, or 15% on amount over £800
Step 3: Other Children Reduction
If you have other children living with you (not in this arrangement), your income is reduced before calculation: 11% for 1 child, 14% for 2 children, 16% for 3+ children.
Step 4: Shared Care Deduction
- 0-51 nights per year: No reduction
- 52-103 nights: 1/7 off (14.3%)
- 104-155 nights: 2/7 off (28.6%)
- 156-174 nights: 3/7 off (42.9%)
- 175+ nights: 50% off minus £7 per child
Why Use Our Calculator?
- Accurate: Uses the exact CMS formula with all adjustments
- Private: All calculations happen in your browser - no data is stored
- Free: The calculator is completely free to use
- Instant: Get results immediately without waiting
PDF Reports
While the calculator is free, we offer optional PDF reports for those who need documentation:
- Basic Report (£4.99): Professional PDF with your calculation breakdown, date stamp, and unique reference ID
- Comprehensive Report (£9.99): Everything in Basic, plus income scenarios, shared care variations, and 18-year projections
Important Notice
This calculator provides estimates only. It is not affiliated with the Child Maintenance Service or UK Government. For official assessments, please contact the CMS directly. Our reports are for reference and planning purposes only.